The present invention pertains to infrared analysis of matter, and more particularly to infrared optical electronic qualitative analysis of a fluid independent of the temperature thereof.
Although the present invention is applicable to qualitative analysis of any type of fluid independent of its temperature, it will be described hereafter specifically in regard to refrigeration, air conditioning, or similar systems using a machine, such as a compressor, requiring a lubricant, such as a petroleum-based oil. For example, in an air conditioning system including a condenser, an evaporator, and a compressor, some type of lubrication is used during operation of the compressor. During the normal course of use, the lubricant will become contaminated as a result of its own decomposition or with water, acid, or other particulates from different parts or areas of the system. Eventually, the lubricant will need to be drained and replaced by new lubricant to maintain efficient operation of the compressor and the system.
Currently, a conventional method of monitoring lubricant quality of a compressor, such as a centrifugal compressor, requires obtaining a sample of the lubricant and sending it to a laboratory for analysis. Generally, this includes a long period of delay in receiving the determined contamination level, and if the results indicate the lubricant is in satisfactory condition, a needless expense has been incurred. Furthermore, the degradation of lubricant may result from a series of occurrences during operation that may not be reflected in the static oil analysis. Therefore, an in situ evaluation or analysis would have the advantage of sensing these impulse occurrences. For example, a momentary leak could inject water into the system at one point in time, and might not be detected by a static oil sample.
An accurate determination of lubricant quality via optical electronics should include correction or compensation for temperature variations within the fluid during operation of the system. One such known method of correcting for temperature variations includes the use of temperature sensing devices, such as thermistors, to detect either one or several temperatures at different points, and then to feed the readings to a control system that would compensate for temperature changes.